[Evans, Marv]

I think the damage (if any) is done. Since no doubt the interviewers already know who will be interviewed, it doesn't seem like it would improve the situation if you withdrew the day of the interview. Ideally an employer can't hold it against you (I said ideally) for wanting to improve your situation. I would think at this point, it would be more prudent to go ahead with the interview and let the chips fall where they may. On the bright side, there is a chance it might work out to your advantage in some ways.